The present invention relates to a coated cutting tool with a wear resistant coating comprising the quarternary alloy Ti—Si—C—N, deposited by physical vapour deposition.
Modern high productivity chip forming machining of metals requires reliable tools with high wear resistance, good toughness properties and excellent resistance to plastic deformation. This has so far been achieved by applying a suitable coating to the surface of a tool substrate. As a result, the tool may be used at considerably higher cutting speed and feed. The coating is preferably hard, wear resistant and stable at high temperatures. The tool substrate is generally in the shape of an insert, for clamping in a tool holder, but can also be in the form of a solid drill or a milling cutter.
Cutting tools are generally optimized for a particular application area, defined by the special requirements on the tool, such as high resistance to crater wear, high resistance to flank wear etc. It is, however, desirable to extend the field of application by improving one or several properties without loss in other properties.
Physical Vapour Deposition (PVD) is a technology known for thin film growth of stable compounds. In the metal cutting industry PVD coatings including layers such as TiN, Ti(C,N) and (Ti,Al)N are among the most common. Evaporation of metal from targets is accomplished by electrical arc or ion bombardment in a reactive gas containing nitrogen or carbon. Very often the targets have the same metal composition as the final layer.
Ma et al. (Thin Solid Films 496 (2006), pp 438-444) and (Surface & Coatings Technology 200 (2005), pp 382 386) disclose depositing Ti—Si—C—N coatings onto high speed steel substrates using plasma enhanced chemical vapour deposition from TiCl4/SiCl4/H2/N2/CH2/Ar mixtures, wherein particularly the hardness behaviour of the deposited coating is evaluated.
Jeon et al. (Surface and Coatings Technology 188-189 (2004), pp 415-419) discloses Ti—Si—C—N coatings deposited on WC—Co substrates by a hybrid system combining the arc ion plating (AlP) and DC magnetron sputtering techniques using Ti and Si targets in an Ar/N2/CH4 gaseous mixture.
H. Xu et al. (Surface & Coatings Technology 201, 2006, pp 4236-4241) discloses deposition of a thick Ti—Si—C—N coating onto a stainless steel substrate in a plasma enhanced magnetron sputtering process using trimethylsilane. A 17 μm thick Ti—Si—C—N coating was fabricated and pin-on-disc tests were conducted in order to evaluate the tribological properties with aluminium and alumina counterparts.
It is an object of the present invention to provide a PVD coated cutting tool for chip forming machining having improved resistance to crater wear, without loss in resistance to flank wear.